The cheapest loose blue diamond I found on blue nile was .31 ct and 15k. Sooo… I think you are limited to the “blue diamond- LOOK” or you can find a plethora of options in white. Blue diamond cluster ring rather than a bigger stone? Aquamarine, Sapphire, or Blue topaz (even with some white diamonds (halo) to provide some extra sparkle and please fiance) would be doable and lovely.

These came from a quick google session- Majestydiamonds.com is the site

@IzzyBear: That’s a great idea, i’ve never seen one in blue! Thanks so much!

@Corgi-cariad: I was hoping for a cusion or asher, not great cuts on a budget lol I will totally check it out, I was thinking of going for a london blue topaz for my ring but i’m scared it wont hold up.

@dewingedpixie: I’m thinking that too! Ruby and Saph are right there in hardness, not a diamond, but i’m not too hard on my ring.

Found these blue diamond rings for you on a quick search. These are all less than $800, top right one is just $449!. Think a genuine blue diamond (or a natural sapphire too) is a great idea! Unique! Good luck.Don’t forget to post a pic of what you ending up getting!